Polyimides exhibit excellent heat resistance and mechanical properties, can be readily formed into films, and can be subjected to surface flattening, and are consequently widely used as surface protective films and interlayer insulation films and the like for semiconductor elements. When such polyimides are used as surface protective films or interlayer insulation films or the like, processes for the formation of through-holes and the like are mainly conducted by etching processes using positive photoresists.
During such processes, the polyimide dissolution rate (etching rate) is an important property in terms of controlling the size of the polyimide portion removed during the etching process. In highly automated semiconductor production processes, fluctuations in the polyimide dissolution rate can have a significant effect on falls in productivity levels and the generation of defects. Accordingly, a method of simply evaluating the polyimide dissolution rate, and a method that enables this evaluation to be conducted on-line or in-line where necessary, are sought. Examples of known methods of evaluating properties include a method of forecasting the properties of product materials, and a method of ascertaining the chemical structural components within a composition (for example, see Japanese translation of PCT international application No. 2000-516342 and Japanese translation of PCT international application No. 2001-508354).